The present application relates generally to medical devices and, more particularly, to medical devices for temporarily occluding body lumens.
Medical devices are often used to facilitate the flow of material as, e.g., in a ureteral stent used for drainage of urine from the kidney to the bladder, or in a vascular graft used to maintain blood flow. However, there are times when it would be preferable to stop flow or occlude a lumen temporarily such as, e.g., to block blood flow until a clot has formed, to block a bodily fluid until a surgery is complete, to block a passageway to protect another part of the body, to block the urethra to prevent urinary leakage or bleeding, to block the fallopian tube or vas deferens to prevent conception, or to block a passageway to compartmentalize pressure or material to one part of the lumen and not another. In many of these cases occlusion is only needed temporarily.
Current occlusion devices, backstops or plugs are often difficult to place, difficult to maintain in position, can be potentially traumatic, and need removal physically to be temporary. Placement of a physical solid plug or similar device may not create sufficient obstruction of the body passageway depending on the nature of the occlusive device. For example, the occlusive device may be incorrectly sized and too small to create complete obstruction, and may be incorrectly shaped for complete occlusion, or be slightly permeable. An occlusive device placed in the fallopian tubes, e.g., might be too small to securely seal against the fallopian tube walls or might be formed of a screen like structure and thus be slightly permeable. It might create an obstruction sufficient to prevent the passage of an egg past the occlusive device, but might in fact be dangerous if sperm, a much smaller cell than the egg, is able to pass the obstruction and fertilize the egg upstream of the obstruction, creating an ectopic pregnancy.
Placement of an occlusive device with a predefined shape may not conform to the lumen, resulting in incomplete obstruction. For example, ureters are not cylindrical, but have irregular cross-sections with multiple folds. A tubular or spherical device, even one that expands may not occlude these folds. Additionally, even if the occlusive device is shaped to fill the entire lumen, fallopian tubes tend to recannalize around an obstruction. Similarly, ureters and vascular lumen can dilate around the occlusive device and thereby resist obstruction.
One method addresses this problem by enhancing tissue ingrowth into the device. However, this may not be practical if the occlusion is to be temporary. Another method is to externally apply pressure to the intended area. For example, in vascular lumens, this method attempts to block flow from the vein or artery until the natural clotting process is complete. Pressure may be manually applied with, e.g., a staple, clip, or clamp. However, this method may damage internal or external tissue and is only viable if access to the lumen is available externally.
Another method addresses temporarily occluding a lumen by using a balloon. Balloons can withstand high pressure. It may be difficult to control the pressure, which can result in overpressurizing or overdilating the balloon, leading to injured tissue. For example, the inflated arterio balloon dilates the artery, potentially injuring the intima, which can lead to thickening and narrowing of the artery.
For patients with urinary fistulas, diversion of urine is performed by a percutaneous transrenal approach with ureteral occlusion. Ureteral occlusion previously was obtained by detachable and non detachable balloons, but migration as well as deflation of the balloons occurred relatively frequently, leading to recurrence of the urine leakage. A silicone ureteral occluder was developed and used with only limited success because of device migration and incomplete ureteral occlusion. It appears that the best results have been accomplished with Gianturco coils and Gelfoam embolization. Even with multiple coil placements, together with Gelfoam plugs, the ureteral occlusion is sometimes achieved for only weeks or months, and was attributed mostly to the induced urothelial hyperplasia. Coil migration was frequently encountered. The lack of an appropriate self-anchoring mechanism results in coil migration, which eventually deteriorates the occlusive effect.
Another method of internally occluding blood vessels is a “T” shaped device with a bulbous tip placed at either end of the “T.” These devices are manufactured from silicon rubber. The bulbous tips of the device are inserted into each of the two parts of the vessel. The bulbous tips have to be correctly sized to effectively occlude the blood vessel. In clinical practice, these devices reduce bleeding at the arteriotomy, but do not stop bleeding.
Percutaneous occlusion techniques have become important tools in minimally invasive management of a wide range of pathological conditions. Use of permanent mechanical occlusion devices, such as coil embolization, has been shown equivalent to that of surgical ligation. The Gianturco-Wallace stainless steel coil (Cook Inc., Bloomington, Ind.) has been a widely used permanent, expandable intravascular occlusion device for transcatheter delivery. The coil and other mechanical occlusion devices have a number of drawbacks, the largest one being that they are typically permanent or implanted, which is undesirable for certain applications.
Other temporary backstops, such as the NTrap (Cook Urological) or Stone Cone (Boston Scientific), are designed to allow certain size fragments to pass through in the ureter. However, in addition to these devices not fully occluding (which may be desirable in certain clinical circumstances), these devices need to be restrained by a wire, tether or the like for retrieval. The restraint may get in the way of other procedures such as laser lithotripsy. The restraint may become detached and additional procedures may be required to retrieve the unconstrained segment of the backstop.
Other device occlusion concerns in body lumens are high flow conditions. A coil anchoring system has been devised for vascular application, however often rendering the system non-repositionable or removable. Additional concerns with existing occlusion devices are the need for specialized equipment, the time required for installation and the complexity of the procedure, all resulting in greater cost to the patient.